Multilayer films are important items of commerce, being particularly useful in packaging, where differing properties offered by various polymers of the film layers are important to the overall functioning of the film in use. The most common method of forming films from thermoplastics is extrusion of the polymer through a film die, and multiple layer films are typically formed by extruding each polymer needed separately, and either joining the individual films in the die or just outside the die, or extruding the various layers through individual dies and then laminating the layers together, or some combination of the two. One concern in the formation of such multilayer films is the adhesion between various layers, particularly when adjacent layers are made from polymers that are unlike each other. Various solutions, such as the use of separate tie ("adhesive") layers have been used, but these involve extra expense. Therefore better methods of making multilayer films are desired.
When LCPs are extruded into films (singly or in multilayer structures), the polymer usually is highly oriented in the machine (extrusion) direction (MD), and is weak and brittle in the transverse direction (TD). Special methods have been developed to produce LCP films (or thin tubes which can be slit into films) with more balanced MD/TD properties, thus improving the TD properties of the film. However, such methods, which for instance are described in U.S. Pat. Nos. 4,384,016, 4,820,466, 4,963,428, 4,966,807, 5,156,785, 5,248,305,288,529, 5,312,238, and 5,326,245 and G. W. Farrell, et al., Journal of Polymer Engineering, vol. 6, p. 263-289 (1986), usually require the use of intricate, expensive equipment which may be difficult to operate reliably, produce tubes which may not lay flat as films, and/or require labor intensive lay-up methods. One of these methods is moving in the TD an extrusion die surface which contacts the molten LCP. Thus better methods of preparing improved LCP films are needed.